Spectrum Chemical manufactures and distributes fine chemicals with quality you can count on including those with CAS number 2538-85-4, Whether you call it Eriochrome� Blue Black R, Calcon , 1-(2-Hydroxy-1-naphthylazo)-2-naphthol-4-sulfonic Acid Sodium Salt , Mordant Black 17 or Palatine Chrome Black R you can be assured the Eriochrome� Blue Black R products offered by Spectrum, meet or exceed the grade requirements or specifications for each individual product.